The invention relates to a vehicle having a drive shaft that is driven by an engine and that transmits torque generated by the engine to a first drive, and having a clutch compressor and a power steering pump. The power steering pump is driven by an output shaft that transmits torque from the first drive to the power steering pump.
The invention furthermore relates to a method for controlling a power steering pump and a clutch compressor in a vehicle having a drive shaft that is driven by an engine and that transmits torque generated by the engine to a first drive, and having a clutch compressor and a power steering pump. The power steering pump is driven by an output shaft that transmits torque from the first drive to the power steering pump.
For the purpose of driving a vehicle, modern vehicles have an engine and a multiplicity of further ancillary assemblies, the interactions of which, firstly, enable the vehicle to operate reliably. Designated as ancillary assemblies in this case are all auxiliary machines of the vehicle that are driven directly or indirectly by the engine and that are necessary or helpful for the operation of the vehicle. Examples of ancillary assemblies are a water pump that supplies the engine with cooling water, a power steering pump that reduces the steering force to be applied, and a clutch compressor, present particularly in the case of commercial vehicles, for boosting the braking force applied by the driver of the vehicle.
Basically, ancillary assemblies can be divided into two categories. A first category of ancillary assemblies comprises all ancillary assemblies whose continuous operation is necessary for the operation of the engine, or of the vehicle. These ancillary assemblies include, for example, a fuel pump and the cooling water pump. A second category of ancillary assemblies comprises all ancillary assemblies that are only temporarily necessary for the operation of the engine, or of the vehicle. These include, for example, a starter, which is required only for starting the engine, the power steering pump, which is required merely for assistance in a steering motion of the vehicle, and the clutch compressor, the operation of which is necessary only when there is no longer an adequate reserve of compressed air. Ancillary assemblies that belong to the first category are usually driven directly by the engine. Ancillary assemblies that belong to the second category can be driven as required, the drive being able to be effected independently of the engine, for example in the case of the starter that starts the engine being driven, via an electric motor, by means of energy stored in a battery. Drive in this case denotes a mechanical device that transmits a torque, or force, applied at a drive shaft, to an output shaft. The drive can be, for example, a gearwheel drive, a belt drive or a chain drive.
Ancillary assemblies consume energy, and therefore contribute to the fuel consumption of the vehicle. To reduce the fuel consumption, it is therefore desirable to operate ancillary assemblies only when they are actually required. On the other hand, the continuous operation of an ancillary assembly can be advantageous, or even prescribed, in respect of safety. The power steering pump belongs to the ancillary assemblies whose continuous operation is advantageous for safety reasons, since a power steering pump, when switched off for a time, can only assist in a time-delayed manner in a steering operation.
There is known the practice of driving the clutch compressor directly through the drive engine and driving the power steering pump via the clutch compressor. Also known is the practice of driving the power steering pump through the drive engine and driving the clutch compressor via the power steering pump. In the case of clutch compressors, in particular, the torque shocks upon clutch engagement are very great, since there is no torque base load present during the disengaged phase of the clutch compressor, for which reason the drives are subjected here to particularly high peak moments.
It is disadvantageous in the case of these drive concepts that, in the case of a defect in which the drive of the ancillary assembly driven directly via the engine fails, the further ancillary assembly driven via this ancillary assembly fails likewise. This is particularly disadvantageous, since, for example, the simultaneous failure of the clutch compressor as an ancillary assembly and of the power steering pump as a further ancillary assembly corresponds to a braking failure with simultaneous loss of steering capability.
There is therefore needed an arrangement of a clutch compressor and power steering pump, wherein the failure of the one ancillary assembly does not automatically entail the failure of the other ancillary assembly and, at the same time, the transmission ratios for driving the clutch compressor and the power steering pump can be selected independently.
This need is met according to the invention by a vehicle having a drive shaft that is driven by an engine and that transmits torque generated by the engine to a first drive. The vehicle includes a clutch compressor and a power steering pump. The power steering pump is driven by an output shaft that transmits torque from the first drive to the power steering pump. A further output shaft, for driving the clutch compressor, is provided. The further output shaft is disposed on a second drive, to which torque is transmitted by the drive shaft that is driven by the engine. The further output shaft transmits torque from the second drive to the clutch compressor.
Expediently, it can be provided in this case that the first drive and the second drive differ. Both the first drive and the second drive are driven by the engine, such that the transmission of the torque to the power steering pump and to the clutch compressor occurs independently in each case in the first drive and the second drive. The failure of the first or second drive therefore does not interfere with the functioning of the ancillary assembly driven via the respectively other drive, such that a significant improvement in safety can be achieved. Moreover, it is possible for the transmission ratio to be selected dissimilarly between the engine and the power steering pump and the clutch compressor, the power steering pump, in particular, being able to be structurally optimized through an adapted displacement volume.
Alternatively, it can be provided that the second drive is identical to the first drive, and the further output shaft is disposed parallelwise in relation to the output shaft on the first drive. The transmission of the torque from the drive shaft to the output shaft and to the further output shaft is effected independently of one another. Likewise, in the case of this possibility for transmitting the torque of the engine to the two ancillary assemblies, a defect, for example of the output shaft driving the power steering pump, does not result in a disturbance of the functioning of the clutch compressor driven by the further output shaft, and vice versa. The transmission ratio likewise are freely selectable. In this way, the operational safety of the vehicle can also be improved. It is possible at the same time to structurally optimize the ancillary assemblies.
Advantageously, it can be provided that the clutch compressor is coupled to the further output shaft via a clutch that can be operated by a control device. Since the operation of the clutch compressor is necessary only when the pressure in a pressure vessel disposed in the vehicle drops below a predefined value, the complete switch-off of the clutch compressor by means of a clutch enables fuel to be saved without endangering the safety of the vehicle.
Expediently, it can be provided that the control device controls at least one further function of an air drier. Further control operations, usually controlled by a second control device, occur in connection with the preparation of compressed air in a vehicle, for example in the case of a regeneration operation of a desiccant used in an air drier. The integration of all functions connected with the clutch compressor and the air drier therefore allows the elimination of electronic components, since the second control device can be dispensed with.
Advantageously, it can be provided that a further control device is provided, which controls the power steering pump. Control operations that can be performed by a further electronic control device also occur in connection with the power steering pump. The further control device is thus independent of the control device that controls the clutch of the clutch compressor, such that a complete redundancy between the power steering pump and the clutch compressor is ensured.
Expediently, it can be provided that the further control device is operatively configured in such a manner that the further control device senses at least the output pressure of the power steering pump. The output pressure of the power steering pump can serve, for example, as a reference point for a defect.
Advantageously, it can be provided that the control device or the further control device is operatively configured in such a manner that the control device or the further control device senses the speed of the vehicle. From the sensed speed of the vehicle, the further control device can infer the output pressure of the power steering pump.
In particular, it can be provided in this case that the further control device is suitable for adapting the displacement volume of the power steering pump in dependence on vehicle speed. The varying of the displacement volume of the power steering pump allows the pressure provided by the power steering pump to be regulated independently of the engine rotational speed. An optimum regulation of the pressure provided by the power steering pump is achievable through superimposition of both adaptation possibilities.
Expediently, it can be provided that the control device and the further control device are operatively configured in such a manner that at least error messages are exchanged between the control device and the further control device. An adapted operation, i.e. an emergency operation, in which all functions of the ancillary assembly not affected by a defect might no longer be available, in order to increase the safety or to fulfill legal requirements, can thus be realized.
Advantageously, it can be provided that the control device is operatively configured in such a manner that the control device calculates switch-off sequences and switch-off pressures for the clutch compressor from the speed of the vehicle. The complete switch-off of the clutch compressor through the clutch when there is an adequate reserve of compressed air allows a maximum saving of fuel during the operation of the vehicle. Since the quantity of air delivered can be inferred from the vehicle speed, synchronization of the air delivery phases of the clutch compressor with expected thrust phases of the engine can be achieved. The utilization of a thrust phase of the engine as an air delivery phase of the clutch compressor is particularly favorable in respect of energy, since fuel is scarcely used in the thrust phases.
Expediently, it can be provided that the further control device is operatively configured in such a manner that the further control device calculates a power steering pressure and the necessary power steering transmission ratio from the speed of the vehicle, an adaptation of the displacement volume of the pump being able to be effected. Both the expected and the required power steering pressure can be inferred from the speed of the vehicle. Thus, for example, a defect of the power steering pump can be detected.
The invention also includes a method for controlling a power steering pump and a clutch compressor in that torque is transmitted from the drive shaft driven by the engine to a second drive, and the clutch compressor is driven by a further output shaft disposed on the second drive.
On this basis, the advantages and particularities of the system according to the invention are also realized by the method for controlling the system.
The method can be developed, advantageously, in that at least error messages are exchanged between a control device that controls a compressor clutch and a further control device that controls the power steering pump.
Furthermore, it can be provided that the control device or the further control device senses the speed of the vehicle.
Expediently, it can be provided that the control device calculates switch-off sequences and switch-off pressures for the clutch compressor from the speed of the vehicle.
Furthermore, it can be provided that the further control device calculates a power steering pressure from the speed of the vehicle.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.